NEEEEEEEED TO KNOW Flashcards
What is the relative atomic mass
Relative atomic mass (Ar) is the weighted mean of the atoms of a normal sample relative to 1/12 the mass of the C-12 isotope
What is the relative isotopic mass
Relative isotopic mass is the mass of an isotope of the element relative to 1/12 the mass of the C-12 isotope
What is relative molecular mass
Relative molecular mass (Mr) is the mass of a molecule relative to 1/12 the mass of the C-12 isotope
What is the relative formula mass
Relative formula mass is the sum of all the atomic masses of all the atoms in a particular formula
What is the molecular/parent ion
the peak with the highest mass caused by the ion formed from the whole molecule
Where to find the molecular ion
the largest peak at the end of the m/z graph
Which metals atom emit coloured flames
lithium
sodium
potassium
calcium
strontium
barium
Definition of first ionisation energy
the energy required to remove one electron from each atom in one mole of gaseous atoms producing one mole of gaseous ions with one positive charge
What does the magnitude of the first ionisation energy tell us
the magnitude tells us about the force of attraction between the nucleus and the outer electrons
trends for first ionisation energies across a period
TREND 1: general increase
TREND 2: little drop from group 2 to 3
TREND 3: little drop from group 5 to 6
TREND 4: big drop from group 0 to 1/ one period to another
Reasons for TREND 1
-increase in nuclear charge
-similar shielding and distance
-attraction between outer e- and nucleus
Reasons for TREND 2
-distance increase from s to p orbital
-same shielding
-attraction between outer e- and nucleus decrease
-(despite higher nuclear charge)
Reasons for TREND 3
-outer electron is group 6 is sharing a p orbital
-repulsion between the electrons in the p orbital
-attraction between outer e- and nucleus decrease
Reasons for TREND 4
-large increase in distance and shielding, into a new electron shell
-attraction between outer e- and nucleus decrease
-(despite higher nuclear charge)
how is the RMM calculated using the graph
the mass value of the molecular/parent ion
how to answer an ionisation energy question
PSDSS
P-protons (no. of)/nuclear charge
S-shielding(no. of)
D-distance from nucleus
S-spin pair repulsion
S-strength of attraction
What is ionic bonding
ionic bonding is the strong electrostatic attraction between oppositely charged ions
what affects ionic bonding
-ionic radius
-ionic charge
How to answer ionic bond strength questions
R - radius (ionic)
C - charge (ionic)
A - [a]energy
define isoelectronic ions
same electron structure
trend for ionic radius down a group
increase in ionic radius down a group
more shells
increase in electron density
trend for ionic radius arcoss a period of isoelectronic ions
-ionic radius decrease
-more protons, attract the elctrons closer
What are ionic compounds arranged in
they are arranged in giant ionic lattices
why are anions bigger than than cations
cations have the same amount protons than its parent ion but less electrons . therefore the attraction of electrons to nucleus is more, so a smaller size.
there is more electron-electron expulsion and lower nuclear charge per electron. the electrons push each other away and make the anion bigger.
what does electron density maps show
it shows the likelihood of finding an electron in the region
ionic compunds at room temperature and why
- most ionic compounds are solids
- not enough energy to overcome the strong electrostatic forces of attraction between the oppositely charged ions
what will many ionic compunds dissolve into and why
- polar solvents like water
- δ+ end of the molecule surround the negative anions
- δ- end of the molecule surround the positive cations
- greater the ionic charge, the less soluble an ionic compound is
what are the factors of how soluble an ionic compound is
- the relative strength of the electrostatic forces of attraction with the lattice
- the attractions between the ions and the polar molecules
what gives the evidence of the existence of ions
- electrolysis
- positive ions are attracted to the negative electrode
- negative ions are attracted to the positive electrode
Why does it matter if an electron is by it-self or paired in an electron shell?
- Two electrons in the same orbital experience a bit of repulsion from each other
- This offsets the attraction of the nucleus, so it is easier to lose an electron
Why is the first ionisation energy of a group 3 less than group 2?
The first ionisation energy of group 3 is less than that of group 2 because removing an electron from a higher energy orbital requires less energy. The electron removed from group 3 is in a p sub shell, which has a higher energy than the s electron in group 2.
Why is the first ionisation energy of group 6 less than that of group 5?
The highest energy electron in both group 5 and 6 is the p sub-level, and group 6 has a higher nuclear charge. However, group 6 has an electron that is spin-pairing, leading to repulsion of the two electrons. making it easier to remove.
What are orbitals?
Orbitals are a region of space within an atom where there is a probability of finding an electron
What is the shape of a P orbital
‘Dumbbell’ shaped
Can appear in groups of 3
What is periodicity?
Trends in the properties of elements repeat in successive periods of the periodic table
what determine same chemical properties in elements
no. of electrons in outer shells
properties of isotopes
similar chemical
different physical
What is covalent bonding
the strong electrostatic attraction between the nuclei and the shared pair of electrons between them
what is bond length
the internuclear distance of two covalently bonded atom
what is the relationship between bond length and strength
longer the length, weaker the strength
shorter the length, stronger the strength